[This article originally appeared in La Voz, the newsletter of the Friends of Las Vegas National Wildlife Refuge, Vol. 14, No. 3, October, 2016]
I would like to start by apologizing for putting a pun in
the title, but I am writing this pre-dawn and I rEGRET nothing. Sorry if that last one flew over your head, it was
pretty owlful, but toucan play at puns better than one
anyway so if you have anything better please email me! Newton told us why it is
when objects go up, they must fall back down. Fall migration is no exception. September and October is a magical time to be
out birding; the hundreds of neo-tropical species that migrate north from the
tropics to breed begin to trickle back southward to warmer climates and their
wintering grounds. For many species, these wintering grounds are really more of
their true home, most spend at least 8 or 9 months of the year in non-breeding
areas. These special birds make the perilous trip and leave their habitat
behind for the temporary glut of food that comes with Temperate North America’s
short summers. Take a Wilson’s Warbler (Cardellina pusilla) for example. These diminutive yellow
warblers pass through our area in spring and continue to the misty forests of
the Pacific Northwest and Canada to sing their songs, make their nests, and
breed. They may have two successful clutches (sets of eggs) over the course of
2 or 3 months, and then the whole family (individually, not like the Griswalds
on a road-trip) begin to head back southward. We in Las Vegas usually start
experiencing this trickle in late August, and it continues into mid-October.
Now an interesting thing to consider is that by breeding, the Wilson’s Warblers
have by definition made more of themselves…potentially many more of themselves.
Some may be preyed upon en route southward, some will hit windows
(see how you can prevent this here),
some will be preyed upon by cats (if you like birds, keep your cats indoors!),
but still many will successfully make the journey, crossing through our
woodlands and safely back to Veracruz, Oaxaca, or Chiapas in Southern Mexico.
 |
| Wilson's Warbler in Las Vegas, NM. September, 2013 |
Every fall when I go out looking for rare eastern migrants I
wade through scores of Wilson’s Warblers, potentially dozens on a good day. Cumulatively
for the month of September this year I saw, according to my records, approximately
121 Wilson’s Warblers. To give that some perspective I saw 21 in May, I think
you get the idea. That excess glut of Wilson's will have to survive the tropical
winter in the presence of snakes, tropical species of raptors, even predatory
insects. Let your mind run wild with the things that live in the dark jungles
of Chiapas or Oaxaca and you get a sense of what these 0.3oz birds will go
through before we see them again in May. Anyway, I like fall migration and the
physics of neo-tropical birds; what goes up must fall back down.
